Arc Baby
by librarat
Summary: AU: sorta. Tsuna has become Vongola Decimo and all is peaceful. Until Tsuna gets pulled into a dream and is told that evil is rising once more, he then gets transformed into an Arcobaleno baby and must protect a new family that has been hiding in the shadows for a very long time...


Prologue

"_**Sawada Tsunayoshi, the direct descendant of Vongola Primo. You are otherwise known as Vongola Decimo as well as Neo Vongola Primo. You were once known as one of the weakest and least intelligent people in this world but now you are one of the strongest. You and your Guardians have changed the Vongola family who strayed so long ago. **_

"_**You even saved the former Arcobaleno from their fate. You have proven your worth and also proven to us that you are the obvious choice…" Sawada Tsunayoshi, also known as the tenth generation Vongola boss, could only stare in slight confusion at the beings that stood taller than anyone he had ever known. They were covered in capes that went from head to toe and wore porcelain masks to conceal their faces. **_

_**The men-he knew they were all men because they had all took turns speaking and unless they were extremely good at mimicking men's voices, they were men until proven otherwise- seemed to look towards one another before looking back down at him. Narrowing his chocolate brown eyes, Tsuna stood straighter as though he were doing negotiations with another boss. He knew now who these people were. Over time, the assassins that had been turned into the Arcobaleno had relayed their stories to him. They knew that he would never judge them and would instead comfort them after they had gotten everything off their chest.**_

_**This was very reminiscent of the story that Reborn had told him about. The one where Luce had been chosen to be the Sky Arcobaleno…**_

"_**The Arcobaleno system was abolished almost ten years exactly. You cannot make me one so I fail to see what you are trying to attempt." He spoke gently but his voice carried throughout the almost pitch black room. **_

"_**We are not trying to bring the system back. We merely believe that you should know about the new threat to our world. But our help has its limits, at this time we are doing our best to hide from the growing evil but it's not so easy…" The man drifted off as he noticed the flame that was starting to burn in Tsuna's eyes.**_

"_**An illusion, one that can't be dispelled until whatever that needs to be taken care of is gone for good; is that what you mean?" At the hesitant nod he received from the leader of the men, Tsuna sighed softly to himself.**_

"_**There is also the chance that I may die, is that correct?" Once more the leader nodded. Closing his eyes, Tsuna lifted a hand to his brow before opening chocolate eyes and seeing the slight twinkle of his Vongola ring. It shone strangely in this room which had no visible light. A chuckle left his lips and he looked back up at the beings before him.**_

"_**You should also know that I will do whatever I can to protect my Famiglia. Please do what you must so I can protect them and everyone else." Tsuna stood straight and almost seemed to be taller than he actually was, he also held his arms at his sides and struggled to keep them limp. After so many years of being in so many unfavorable situations it was now his instinct to fight-and keep his true strength back- against someone that even had the slightest hint of harming him.**_

_**The tenth generation boss knew that these people wouldn't mean to harm him, but his ingrained instincts were much harder to convince. Thankfully, his Hyper Intuition kicked in and threw his instincts down. **_

_**The men were now chanting something in a language he knew far too well.**_

"_**This man who protects all whom he loves, grant him the form that seems harmless but hides the true warrior deep within. Let him protect and cherish those he loves and grant him strength and will to save this world from doom and chaos."**_

_**And all at once Tsuna was hit with a blinding array of light that was remarkably similar to his Sky flames. His body felt as though it was burning and he tensed with the strain of not moving and attacking those that dared to inflict such agony onto him. Tsuna was sure that he screamed multiple times but fell silent when he collapsed to the ground.**_

_**The beings neared him and he heard the words, "Be well, Precious One," before utter oblivion took over and his eyes closed unwillingly so he could sleep off what had been done to him…**_

The Vongola Guardians, Varia, former Arcobaleno, and the Simon Famiglia all bolted out of their beds upon hearing a horrifyingly gut-wrenching scream that was coming from Tsuna's room. All of them hurried out of their own rooms and practically trampled each other to get into Tsuna's.

Xanxus, Reborn, Hayato, Enma, and Mukuro were the ones that made it to his room first. They scanned the room suspiciously before moving to the large bed where a small lump could be spotted under the blankets. Enma was the one who took the plunge and ripped the blankets from the bed only to stare in confusion at the small person on the bed.

Reborn pushed Enma out of his way as soon as he saw and climbed onto the bed where the shaking figure rested.

"Oi, Tsuna, wake up!" Reborn called almost frantically and watched almost nervously when Tsuna opened his eyes drowsily.

The formerly petite boss was now the size of an Arcobaleno baby!

"Re-Reborn, now I know why it hurt so much." Tsuna stuttered tiredly in his now high pitched voice as he shifted his small body to sit up.

"Tenth, are you alright?! Why did this happen, do I need to blow someone up?" Tsuna smiled at his right hand's excitability, Hayato never changed when it came to his boss's well-being and while Tsuna was grateful that the Storm Guardian cared so much, he was also a bit worried.

"No Hayato, this was done with my full consent and before you ask Mukuro, it is an illusion, but one that cannot be broken. For all intents and purposes, I am now the Arcobaleno Guardian as they called me and my true body will not be given back until I accomplish what I am meant to do."

The people in his room and crowding outside of it could only listen in shock. What did Tsuna mean? Arcobaleno Guardian, what the hell was that supposed to mean?

"Oi, Vongola Boss, explain and explain now!" Xanxus was the one who had broken the silence by picking up his boss by the rather loose shirt he had worn to bed and watching as Tsuna struggled to keep the shirt on and not fall because he knew that the temperamental man that he trusted to lead Varia would definitely drop him.

Tsuna sighed mentally at the name he was called, though he supposed it was definitely better than being called 'Vongola trash' like Xanxus used to call him. "Xanxus, please don't drop me, I'm already in too much pain as it is." Tsuna said pitifully as large chocolate brown eyes started to fill with tears. Thankfully, Hayato deftly grabbed the baby-sized Tsuna and cradled his beloved boss in his arms and watched in slight glee as the Varia leader huffed irritably.

"Tenth, please explain what you mean by 'Arcobaleno Guardian,' we already got rid of the Arcobaleno system so what is happening?"

"I don't exactly know myself but something bad is happening, there are people who are threatening this world's peace and I was chosen to protect it; and with it, this as well." Tsuna pulled out a pacifier that had been hidden by his now oversized shirt and everyone stampeded into the room to look at it. It was an array of colors, going from vivid red to sunny yellow, flashing green to stunning blue, hazy indigo to serious purple in a pattern only to become shocking white at the end of each sequence.

"From what I can gather, the 'Arcobaleno Guardian' that I am supposed to be means that I am to protect a certain person, or Famiglia. Do you remember, Takeshi, the new Famiglia that has started to turn heads?" Calm brown eyes turned to the Rain Guardian and Takeshi felt himself straighten immediately and go from fun-loving to coldly serious in a mere moment.

"Yeah, I remember. That was what our business trip was about three weeks ago. The Arc Family right Tsuna?" The Rain Guardian felt something cold go down his spine; the others didn't know exactly what happened on that trip except for Tsuna and him. God, just thinking about the Arc Family made him wince. He had come face to face with Giovanni; the young man was a skilled fencer from what he had seen but far too bloodthirsty.

Tsuna and him had had to interfere when they had come upon the scene of Giovanni absolutely slaughtering the men that had tried to kill him and then had been about to kill a poor innocent child who had stumbled onto the gruesome carnage.

The Vongola boss was quick to subdue the young Mafioso but after sending the poor girl home, Giovanni had stunned Takeshi when Tsuna wasn't looking and got away from them as quick as possible.

"No, their true name is the Arcobaleno Famiglia, at least, it was called that when they first formed but shortened it to 'Arc' five generations later. We have to protect them." Tsuna's gentle but high voice carried over to him and the Guardian of Rain saw that he had worried his boss when he had gone silent.

Everyone else besides Reborn were watching the two curiously, obviously this 'Arc Family' was to be taken seriously if one of the least serious of the Guardians was reacting so seriously at just the mention of them.

Tsuna gestured for Reborn to take him and Hayato unhappily handed the small boss to the world's greatest hitman. "Reborn, we need to speak in private."

The hitman sighed under his breath and took Tsuna to the Vongola Decimo's office before soundly shutting the door in everyone else's faces. Taking the time to scoff at them, he placed the Decimo on his desk before giving the entirety of his attention to the Neo Primo as he liked to call his former student.

* * *

So, this is somewhat of an AU story, and I actually thought of it when I was waking up. I don't know whether or not everyone will like it, but I love KHR and decided I had to write a story too. Anyways, I hope everyone likes it.

Disclaimer: I don't own KHR at all and I'm not getting paid to write this.


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